The primary function of the human immune system is to protect an individual against infection by foreign invaders such as microorganisms or viruses. However, it may happen that the immune system attacks an individual's own tissues, leading to pathologic states known as autoimmune diseases, which are frequently associated with inflammatory processes.
According to a commonly used classification, CD4+ T-cells can be assigned to two different subsets called T helper type 1-cells (Th1) and T helper type 2-cells (Th2) on the basis of distinct, non-overlapping cytokine expression patterns. Th1 is characterized by the secretion of IL-2, interferon-γ, IL-12 and TNF-α, and Th2 by the secretion of IL-4, IL-5, IL-9, IL-10 and IL-13. In spite of this general categorization, these are not strict subsets as IFN-γ and IL-10 can suppress effects associated with Th1 as well as Th2 responses, and IL-4 and IL-13 are also able to promote the production of IL-12, thereby promoting Th1 and potentially inhibiting Th2 responses. Th1 T-cells are able to mediate macrophage activation and delayed-type hypersensitivity (DTH), giving rise to pro-inflammatory or cell-mediated immune responses, whereas Th2 T-cells promote IgG1 and IgE secretion leading to immediate-type hypersensitivity reactions (humoral immunity; stimulation of antibody-mediated responses, activation of mast cells, and tissue eosinophilia). Th1 is a key feature in the pathogenesis of diseases like rheumatoid arthritis, sarcoidosis, and tuberculosis, whereas Th2 is involved in allergy, antiparasite responses and in the asthmatic airway.
Inflammation is the body's basic response to a variety of external or internal insults, such as infectious agents, physical injury, hypoxia, or disease processes in nearly any organ or tissue in the body. Inflammation entails the four well-known symptoms, namely redness, heat, tenderness/pain, and swelling. More specifically, inflammation involves assembly of immune system cells and molecules at a target site. Examples for chronic inflammatory diseases are rheumatoid arthritis, inflammatory bowel disease, systemic lupus erythematosus, multiple sclerosis, and type 1 diabetes, for example. These diseases are also often characterized as autoimmune diseases or autoimmune/inflammatory disorders.
As mentioned above, an autoimmune disease is a condition in which the body recognizes its own tissues as foreign and directs an immune response against them.
There are many different autoimmune diseases, and they can each affect the body in different ways. For example, the autoimmune reaction is directed against the brain in multiple sclerosis and the gut in Crohn's disease. In other autoimmune diseases such as systemic lupus erythematosus (lupus), affected tissues and organs may vary among individuals with the same disease. One person with lupus may have affected skin and joints whereas another may have affected skin, kidney, and lungs. Ultimately, damage to certain tissues by the immune system may be permanent, as with destruction of insulin-producing cells of the pancreas in Type 1 diabetes mellitus.
Rheumatoid arthritis is a disease marked by signs and symptoms of inflammation of the joints. Systemic lupus erythematosus (SLE) is characterized by red, scaley patches on the skin and by malfunction of the kidneys at the advanced stage of the disease, and is associated with inflammatory reactions triggered by deposition of immune complexes in blood vessels, particularly in the kidneys. Multiple sclerosis is a disease characterized by chronic or by relapsing, inflammatory conditions that can cause weakness, body tremors and, in extreme cases, paralysis, and is associated with immune system attack of the protective myelin sheath surrounding peripheral nerve cells. Allergic inflammation is consistent with a Th2-cell-based aetiology of atopic disease. For example, defective priming of Th2 cells in the absence of IL-4 resulted in a failure to generate allergic inflammatory responses after subsequent airway challenge. IL-5 and IL-13 have been shown to be more directly responsible for the characteristic eosinophil infiltrates and mucus hypersecretion.
In multiple sclerosis, Th1 mediated immune responses are thought to promote the disease, whereas Th2 mediated immune responses are believed to have an ameliorating effect on the progression of the disease. T cells expressing IL-10 have been shown to suppress experimental autoimmune encephalomyelitis (EAE), a rat model for multiple sclerosis. TNF-α, has been hypothesized to be responsible for the induction of EAE (TNF-α, can be secreted by both Th1 and Th2 cultures).
Human systemic lupus erythematosus (SLE) is believed to be driven by a Th2 response. However, IFN-γ has been shown to have a major effect on disease progression in a mouse model, whereas IL-4 is expected to mediate disease maintenance.
Myocarditis is defined by inflammation of the heart muscle and is thought to be mediated by an autoimmune response to a cardiac-specific antigen after an acute upper respiratory infection. The severity of the experimental autoimmune myocarditis (EAM) in the mouse model is reduced by administration of anti-IL-4, indicating a role of IL-4 in disease progression.
Examples of autoimmune diseases are given in Table I.
TABLE IExamples of Autoimmune Diseases:Nervous System:Multiple sclerosisMyasthenia gravisAutoimmune neuropathies, e.g. Guillain-BarréAutoimmune uveitisBlood:Autoimmune hemolytic anemiaPernicious anemiaAutoimmune thrombocytopeniaBlood Vessels:Temporal arteritisAnti-phospholipid syndromeVasculitides such as Wegener's granulomatosisBehcet's diseaseSkin:PsoriasisDermatitis herpetiformisPemphigus vulgarisVitiligoGastrointestinal System:Crohn's DiseaseUlcerative colitisPrimary biliary cirrhosisAutoimmune hepatitisEndocrine Glands:Type 1 or immune-mediated diabetes mellitusGrave's DiseaseHashimoto's thyroiditisAutoimmune oophoritis and orchitisMultiple Organs, including the MusculoskeletalSystem:*Rheumatoid arthritisSystemic lupus erythematosusMultiple Organs Including the MusculoskeletalSystem:*SclerodermaPolymyositis, dermatomyositisSpondyloarthropathies such as ankylosingspondylitisSjogren's syndrome*These diseases are also called connective tissue (muscle, skeleton, tendons, fascia, etc.) diseases.
CD164 is a member of the mucin-like receptor or sialomucin superfamily of glycoproteins. Sialomucins are transmembrane glycoproteins ranging from 50-3000 kD exhibiting limited similarity at the cDNA and amino acid levels. Mucin-like expressed proteins share the common characteristic of bearing numerous O-glycosylations linked to serine and threonine residues, which infer multiple kinds of cell-cell or cell-extracellular matrix interactions. Functions of mucin receptors depend on cell types and states of activation correlated with the core mucin peptide and with the cell-specific expression of glycosyl transferases, which in turn regulate the structure and presentation of the O-linked oligosaccharide side chains, membrane anchorage, signal transduction abilities and or/the trafficking of the mucin to the correct cellular domain.
Human CD164 is an ortholog of murine MGC-24v (M. musculus) and rat endolyn (R. norvegicus), a membrane protein located in the lysosomal and endosomal compartment of mammalian cells. Isoforms, domains and the subcellular distribution of CD164/endolyn, have been described (Chan et al., 2001).
In its native state, human CD164 is a disulphide-linked homodimer of two 80-85 kDa subunits. CD164 is highly glycosylated, containing both O- and N-linked glycans. The extracellular region is comprised of two mucin domains (I and II) linked by a non-mucin domain containing intra-disulphide bridges as well as a cysteine-rich motif that resembles a consensus pattern previously found in growth factor and cytokine receptors. CD164 also contains a transmembrane domain and a 13-amino acid intracellular region that includes a C-terminal motif (i.e. YHTL) able to target the protein to endosomes and lysosomes.
Four human CD164 mRNA species have been described arising by alternative splicing of six bona fide exons from a single genomic transcription unit located on human chromosome 6q21 (Zannettino A, 2001; Watt and Chan, 2000).
The predominant CD164 (E1-6) isoform represents a 178 amino acid type I transmembrane glycoprotein. The other described isoforms are a sialomucin CD164 or CD164 isoform delta 5 containing 178 amino acids; a 184 residues CD164 isoform delta 4; and a 200 kD principally soluble isoform termed MGC-24 (for Multi-Glycosylated Core protein of 24 kD) lacking the transmembrane anchoring motif and having 189 residues. All isoforms are highly glycosylated proteins with O- and N-linked glycosylation sites.
CD164 functions include mediating, or regulating, haematopoietic progenitor cell adhesion and the negative regulation of their growth and/or differentiation. CD164 is usually expressed by CD34+ and CD34lo/− haematopoietic stem cells and associated microenvironmental cells (Watt et al., 1998). CD164 is also expressed by committed myeloid and erythroid colony forming cells, on bone marrow stromal and endothelial cells, weakly on lymphocytes, and on mesenchymal stem cells. CD164 may play a key role in haematopoisesis by facilitating the adhesion of human CD34+ cells to bone marrow stroma and by suppressing CD34+CD38lo/− haematopoietic progenitor cell proliferation, acting as a potent signaling molecule (Zannettino et al., 1998).
These effects involve the CD164 class I and/or II epitopes recognized by the monoclonal antibodies (mAbs) 105A5 and 103B2/9E10. The epitopes are carbohydrate-dependent and are located on the N-terminal mucin domain I (Watt et al., 2000; Doyonnas et al., J Immunol, 165: 840-851, 2000). The interaction of haemotopoietic cells with stromal/endothelial cells in their immediate microenvironment is thought to be of major importance in the regulation of haematopoietic stem self-renewal, quiescence, commitment and migration. These interactions involve cooperation between adhesion receptors, their cognate ligands and cytokines. A range of cell adhesion molecules (CAMS) including the Ig, integrin, cadherin, selectin and mucin-like protein families, participate in these processes.
CD164 also has a role in myogenic differentiation (Lee et al., 2001). Overexpression of CD164 in myoblast cell lines accelerated expression of biochemical markers of differentiation and enhanced formation of multinucleate myotubes, whereas antisense CD164 or soluble extracellular regions of CD164 inhibited myogenesis.
The peanut agglutinin (PNA)-binding site of soluble MGC-24 represents a tumor associated carbohydrate marker expressed in many carcinomas. Total MGC-24 mRNA was found to be lower in human colorectal carcinomas as compared with normal adjacent mucosal tissues (Matsui et al., 2000). Lymphatic vessel invasion by the carcinoma was correlated to low levels of MGC-24 mRNA in colon carcinomas, whereas high levels did correlate with less venous invasion and less remote metastasis. Monoclonal antibodies specific for CD164 are said to be useful for cancer diagnosis or therapy and haematopoiesis inhibition (EP889054, EP761814).
WO 02/098917 discloses the protein NOV25 (SEQ ID NO: 8; FIG. 1B) comprising a sequence 80% homologous with the mature form of the extracellular domain of human CD164.
EP1033401 discloses a protein (SEQ ID NO: 7582) comprising a sequence identical to the mature form of the extracellular domain of human CD164 (SEQ ID NO: 7; FIG. 1B).
The biological activities and therapeutic utilities of the CD164-like proteins disclosed is these prior art documents have not been analyzed.